The present invention relates to a method for driving a plasma display panel for use in image display of televisions, computers, and the like.
FIG. 5 is a partially cutaway perspective view of a conventional AC-type plasma display panel (hereinafter, abbreviated as panel). In the figure, a plurality of pairs of parallelly disposed scanning electrodes SCN.sub.1 to SCN.sub.N and sustaining electrodes SUS.sub.1 to SUS.sub.N are formed on the bottom surface of a first insulation substrate 1, and covered with a dielectric layer 2 and a protective layer 3. Data electrodes D.sub.1 to D.sub.M are formed on a second insulation layer 6 provided opposing to the first insulation substrate 1. Partition ribs 8 are provided between the adjoining data electrodes D.sub.1 to D.sub.M so as to be parallel to the data electrodes D.sub.1 to D.sub.M. A phospher 9 (shown only partly) is provided on the surfaces of the data electrodes D.sub.1 to D.sub.M. The first insulation substrate 1 and the second insulation substrate 6 are opposed to each other with a discharge space 10 therebetween so that the data electrodes D.sub.1 to D.sub.M are orthogonally aligned to the scanning electrodes SCN.sub.1 to SCN.sub.N and the sustaining electrodes SUS.sub.1 to SUS.sub.N. An image is displayed by sustaining discharge between the scanning electrode SCN.sub.i and the sustaining electrode SUS.sub.i that are paired with each other ("i" is an arbitrary number among 1 to N).
FIG. 6 is a view showing an electrode arrangement of this panel. The electrode arrangement of this panel is a matrix with M columns and N rows. M columns of data electrodes D.sub.1 to D.sub.M are arranged in the column direction, and N rows of scanning electrodes SCN.sub.1 to SCN.sub.N and sustaining electrodes SUS.sub.1 to SUS.sub.N are arranged in the row direction.
Hereafter, description is made as to operation of the conventional AC-type plasma display panel. Although not shown, a pulse generator is provided for each of the sustaining electrodes SUS, the scanning electrodes SCN and the data electrodes D, and the output terminal of each pulse generator is connected to the corresponding electrode so that a pulse voltage is applied to the electrode. Respective ground terminals of the pulse generators are connected to a common terminal, and a voltage of difference among the output voltages of the pulse generators is applied to the sustaining electrodes SUS, the scanning electrodes SCN and the data electrodes D. FIG. 7 is a timing chart in the driving operation. In FIG. 7, first, during a writing period, all the sustaining electrodes SUS.sub.1 to SUS.sub.N are held at 0(V) ((V) represents volt). A positive writing pulse voltage +V.sub.W (V) is applied to a predetermined one of the data electrodes D.sub.1 to D.sub.M (hereinafter, referred to as predetermined data electrode D.sub.1 -D.sub.M), and a negative scanning pulse voltage -V.sub.S (V) is applied to the first scanning electrode SCN.sub.1. Consequently, writing discharge occurs at the intersection of the predetermined data electrode D.sub.1 -D.sub.M and the first scanning electrode SCN.sub.1, and a positive charge accumulates on the surface of the protective layer 3 on the first scanning electrode SCN.sub.1 at the intersection. Then, the positive writing pulse voltage +Vw(V) is applied to another predetermined data electrode D.sub.1 -D.sub.M, and the negative scanning pulse voltage -V.sub.S (V) is applied to the second scanning electrode SCN.sub.2. Consequently, writing discharge occurs at the intersection of the predetermined data electrode D.sub.1 -D.sub.M and the second scanning electrode SCN.sub.2, and a positive charge accumulates on the surface of the protective layer 3 on the second scanning electrode SCN.sub.2 at the intersection. Similar scanning operations are continuously performed, and lastly, the positive writing pulse voltage +V.sub.W (V) is applied to still another predetermined data electrode D.sub.1 -D.sub.M, and the negative scanning pulse voltage -V.sub.S (V) is applied to the N-th scanning electrode SCN.sub.N. Consequently, writing discharge occurs at the intersection of the predetermined data electrode D.sub.1 -D.sub.M and the N-th scanning electrode SCN.sub.N, and a positive charge accumulates on the surface of the protective layer 3 on the N-th scanning electrode SCN.sub.N at the intersection.
Then, during a sustaining period, first, a negative sustaining pulse voltage -Vm(V) is applied to all the sustaining electrodes SUS.sub.1 to SUS.sub.N, so that sustaining discharge starts between the scanning electrodes SCN.sub.1 to SCN.sub.N and the sustaining electrodes SUS.sub.1 to SUS.sub.N at the intersections where writing discharge occurred. Then, after a period T from the termination of the negative sustaining pulse voltage -Vm(V) applied to the sustaining electrodes SUS.sub.1 to SUS.sub.N, the negative sustaining pulse voltage -Vm(V) is applied to all the scanning electrodes SCN.sub.1 to SCN.sub.N. Consequently, sustaining discharge again occurs between the scanning electrodes SCN.sub.1 to SCN.sub.N and the sustaining electrodes SUS.sub.1 and SUS.sub.N at the intersections where writing discharge occurred. The words "termination of a pulse voltage" means a point of time when the rising edge of the pulse voltage reaches 0(V). Further, after the period T from the termination of the negative sustaining pulse voltage -Vm(V) applied to the scanning electrodes SCN.sub.1 to SCN.sub.N, the negative sustaining pulse voltage -Vm(V) is applied to all the sustaining electrodes SUS.sub.1 to SUS.sub.N. Consequently, sustaining discharge further occurs between the scanning electrodes SCN.sub.1 to SCN.sub.N and the sustaining electrodes SUS.sub.1 to SUS.sub.N at the intersections where writing discharge occurred. By applying the negative sustaining pulse voltage -Vm( V) alternately to all the scanning electrodes SCN.sub.1 to SCN.sub.N and to all the sustaining electrodes SUS.sub.1 to SUS.sub.N at intervals of the period T in a like manner, sustaining discharge continuously occurs. Light emitted by this sustaining discharge is used for display. The waveform of the negative sustaining pulse voltage -Vm(V) is trapezoidal as shown in FIG. 8 because it takes a predetermined time for the voltage to rise or fall.
Lastly, during an erasing period, a positive narrow time-width erasing pulse voltage -Ve(V) is applied to all the sustaining electrodes SUS.sub.1 to SUS.sub.N, so that erasing discharge occurs. This stops the discharge. By the above-described operation, an image is displayed on the AC-type plasma display panel.
In the sustaining pulse voltage alternately applied to the scanning electrodes SCN.sub.1 to SCN.sub.N and to the sustaining electrodes SUS.sub.1 to SUS.sub.N, it is conventionally considered that after the period T from termination of the application of the sustaining pulse voltage to one of the scanning electrode and the sustaining electrode, the sustaining pulse voltage must be applied to the other electrode. The period T is normally set to 0.5 microsecond or longer. In the above-described conventional panel, the period T is 0.5 microsecond.
In the above-described sustaining discharge operation, during the period T, sustaining discharge necessary for display occurs between the scanning electrodes SCN.sub.1 to SCN.sub.N and the sustaining electrodes SUS.sub.1 to SUS.sub.N. The invertors of the present invention found that erroneous discharge not contributing to display also occurs between the data electrodes D.sub.1 to D.sub.M and the scanning electrodes SCN.sub.1 to SCN.sub.N or between the data electrodes D.sub.1 to D.sub.M and the sustaining electrodes SUS.sub.1 to SUS.sub.N in concurrence with occurrence of the sustaining discharge. This was confirmed from a current flowing through the data electrodes D.sub.1 to D.sub.M during the sustaining period. The erroneous discharge weakens the sustaining discharge, so that the sustaining discharge stops or becomes unstable. Further, since current flows through the data electrodes D.sub.1 to D.sub.M because of the erroneous discharge, ions generated during the erroneous discharge have an impact on the phospher. This deteriorates the phospher, so that the luminance of the sustaining discharge significantly decreases. These two have been problems to be solved.